Approximately 115,000 Americans are currently awaiting organ donations. Their conditions range from heart disease, to cancer, to birth defects, to combat injury. While approximately 80 Americans per day receive organ transplants, another 18 per day die waiting for a healthy matching organ. (U.S. Department of Health and Human Services, Organ Procurement and Transplantation Network; http://optn.transplant.hrsa.gov/)
While there is a need for more donors, there is also a need for better methods of preserving donated organs and assessing viability between harvest and transplant. In some cases, organs expire for purely logistic reasons, that is, they cannot be delivered to the intended recipient within the mandated time frame. For example, hearts that are preserved by cold static storage (e.g., ice chest) cannot be transplanted after four hours of ischemia (lack of blood supply) for fear that the heart will not function in the recipient. Accordingly, weather and traffic delays can cause an otherwise “perfect match” organ to go unused. The short-comings of cold static organs storage have been addressed by a number of recent innovations, such as those disclosed in U.S. patent application Ser. No. 13/420,962, “Apparatus for Oxygenation and Perfusion of Tissue for Organ Preservation,” filed Mar. 15, 2012, and incorporated herein by reference in its entirety.
The “time window” for organ transplant is somewhat arbitrary, however, because the overall health of the donor organ may vary substantially at the time of harvest. For example, the heart of a 50 year old man who died of Alzheimer's will likely not fare as well in ischemic conditions as the heart of an 18-year-old athlete who died in a traffic accident. Certainly, if it were possible to assess the viability of organs during and/or after transport, more organs would be transplanted that were outside the standard transport window.
In addition to monitoring the viability of “healthy” donor organs, reliable assessment techniques could also increase the total number of available donor organs. As discussed above, the demand for donor organs far exceeds the supply. This discrepancy has prompted doctors to re-assess what constitutes a harvestable organ. For many years, organs were only considered for transplant if cardiac death had not preceded harvest or if harvest took place immediately after cardiac death, so-called “beating-heart” donors. Accordingly, donor organs were typically only harvested from patients who died in a hospital capable of providing life support at the time of death.
New research into expanded criteria donors (ECD) and donation after cardiac death (DCD) suggest that many organs that are discarded may be viable for transplant. For example, kidneys are now harvested and transplanted from donors who are over age 60, or over age 50 with a history of hypertension. Additionally, kidneys may be harvested from donors who arrive at the hospital with continued resuscitation after cardiac arrest, but no indication of survival. Kidney donations, in particular, have pushed the limit for donor harvest because a recipient undergoing an unsuccessful transplant can be kept on dialysis indefinitely until a new match is identified.
Nonetheless, doctors have successfully harvested livers from the ECD and DCD groups, and many advocate that this pool of donors is further expanded to include lungs, pancreases, and even hearts. See Steinbrook, “Organ Donation After Cardiac Death,” New England Journal of Medicine, 357; 3, 210-13 (2007). Systems capable of increasing the transport time of organs while also monitoring the viability of the organs could substantially increase the pool of available organs.